1. Field of Invention
This invention relates to ink marking devices, and more particularly to a system and method by which maintenance fluid used by a maintenance station in maintaining a printhead of the ink marking device is replenished.
2. Description of Related Art
Maintaining optimum performance in an ink marking device requires maintenance, particularly of the printhead that expels the ink to mark the media as desired by the user.
Liquid ink printers of the type frequently referred to as continuous stream or as drop-on-demand, such as piezoelectric, acoustic, phase change wax-based or thermal, have at least one printhead from which droplets of ink are directed towards a medium, e.g., a recording sheet. Within the printhead, the ink is contained in multiple channels. Power pulses cause the droplets of ink to be expelled as required from the orifices or nozzles at the end of the channels.
In a thermal ink jet marking device or printer, the power pulses are usually provided by resistors positioned in respective channels that are individually addressable to heat and vaporize ink in the channels. As voltage is applied across a selected resistor, a vapor bubble grows in the associated channel and initially bulges from the channel orifice before collapsing. The ink within the channel then retracts and separates from the bulging ink, forming a droplet moving in a direction away from the channel nozzle and toward the medium. Upon hitting the medium, the droplet forms a dot or spot of ink. The channel is then refilled by capillary action, which draws ink from an ink supply container.
The ink jet printhead may be incorporated into either a carriage type printer (i.e., a partial-width array type printer) or a page-width array type printer. The carriage type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead can be attached to a disposable ink supply cartridge. The printhead and attached ink supply carriage are reciprocated together on the carriage to print one swath of information (equal to the length of a column of the nozzles) at a time on a stationary medium. After the swath is printed, the paper is stepped forward a distance equal to the height of the printed swath or a portion thereof, so that the next printed swath is contiguous or overlapping with the previously printed swath.
In contrast, the page-width array printer has a stationary printhead having a length sufficient to print across the width or length of a recording sheet. The recording medium is continually moved past the page-width array printhead in a direction substantially normal to the printhead length and at a constant or varying speed during printing.
It has been recognized that the ink ejecting nozzles of the printhead must be maintained, e.g., by periodically cleaning the orifices when the printhead is in use, and/or by capping the printhead when the printer is not in use or is idle for extended periods of time. The capping of the printhead prevents the ink in the printhead from drying out and potentially clogging the nozzles. In particular, a "viscous plug" of partially dried ink in the nozzle can cause the ejector to fail, at least temporarily, until the particular ejector is reheated and the viscous plug is softened and expelled. Ink droplets from a partially blocked ejector can be misdirected. The failure of even one nozzle will have conspicuous results on a printed swath, because the plugged nozzle will leave a blank stripe where ink should have been deposited. In some applications, there is also a need to prime a printhead before use to insure that the printhead channels are completely filled with ink and contain no contaminants or air bubbles.
With any kind of ink jet marking device in which a printhead is in close and extended contact with a medium, such as a sheet of paper marked with partially-dried ink, an important practical concern is contamination of the area around the ejectors. External debris such as lint or stray paper fibers are likely to become caught in the small gap between the front face of the printhead and the sheet, possibly entering the nozzles of the ejectors and causing a failure.
Conventional maintenance stations perform two primary functions. In a first function, the printhead nozzles are maintained by wiping clean the nozzle face of the printhead to remove any contaminants or ink which may have collected on the nozzle face. In some applications, vacuum is also applied to assist in removing of the ink and contaminants. In the second function, the printhead is capped to prevent the printhead nozzles from being exposed to air for extended periods of time.
Regarding the first function, wiping using wet wiper nozzles is known. As disclosed in, e.g., U.S. Pat. No. 5,790,146 to Anderson, which is commonly assigned and is incorporated herein by reference, wet wiper nozzles apply a small amount of maintenance fluid to the nozzle face. The wet wiper nozzles remain spaced from the nozzle face, but a thin film of maintenance fluid is applied on the nozzle face through the formation of a meniscus. The maintenance fluid is substantially comprised of water, but may include small amounts of dissolved detergents. Examples of other conventional maintenance systems and components thereof are disclosed in commonly assigned U.S. Pat. Nos. 5,534,897, 5,757,398 and 5,793,390, which are incorporated herein by reference.
In the case of partial-width array marking devices, the wiper nozzles are generally stationary, and the motion of the printhead moving past the wiper devices completes the wiping operation. With a full-width array printhead, the wiping devices are moved past the stationary printhead.
When wet wiper nozzles are used, the maintenance fluid is consumed. As a result, this maintenance fluid must be replenished over time. Depending upon the particular configuration of the marking device, refilling and/or replenishing the reservoir for the maintenance station can be difficult, and/or lead to problems with other systems in the marking device. Therefore, it would be desirable to provide a system and method by which the maintenance fluid could be replenished. In addition it would be desirable if the maintenance fluid could be replenished through use of by-products from the normal operation of the ink marking device to reduce costs and waste.